JPH11223216A - Bearing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pre-load variable bearing unit which can retain excellent bearing performance by suppressing pre-load fluctuation caused by the change of a temperature, and at the same time, can easily change and adjust pre-load and can easily avoid resonance with a product assembled. SOLUTION: This bearing unit is equipped with voltage control means 13 controlling voltage applied to an outer side cylindrical part 6 retaining the even number of rolling bearings 4 and an electrostrictive element 12 arranged on the axial end surface of one cylindrical part of an inner side cylindrical part 2, the cylindrical parts 2, 6 are held and fixed together with the electrostrictive element 12 by bearing unit mounted parts 7, 8, and pre-load can be adjusted by extending and shrinking the electrostrictive element 12 by the voltage control means 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing unit used for supporting a precision rotating part, and more particularly to a bearing unit capable of coping with a change in preload of a rolling bearing due to a temperature change or the like.

[0002]

2. Description of the Related Art For example, spindle motors, rotary actuators, rotary encoders, and the like used in video tape recorders, hard disk drives, laser beam printers, and the like have a precision rotating portion that rotates with high precision. When a rolling bearing is used in a device requiring such high-precision rotation, a bearing unit that applies a preload by using a pair of rolling bearings is often adopted.

FIG. 3 shows a conventional example of a bearing unit for supporting such a precision rotating part. The bearing unit 1 includes an inner cylindrical portion 2 and an outer cylindrical portion 6 rotatably supported on the outer circumference of the inner cylindrical portion 2 via a rolling bearing 4 fitted on the outer circumference of the inner cylindrical portion 2. Configuration. Then, the inner cylindrical portion 2 is fixed to the base 7 with fixing screws 8. The fixing screw 8 includes a shaft portion 8a through which the inner cylindrical portion 2 is inserted, a screw portion 8b which is provided at a distal end of the shaft portion 8a and is screwed to the screw portion 7a of the base 7, and a base end of the shaft portion 8a. A head 8 equipped to hold the end face of the inner cylindrical portion 2
and c are integrally formed.

In the bearing unit 1 described above, the outer cylindrical portion 6
Is a portion that supports the above-described precision rotating portion (for example, a rotation drive unit of a magnetic disk or an optical disk). And
In order for the above bearing unit 1 to exhibit high-precision bearing performance corresponding to the bearing of the precision rotating part, the gap between the rolling ball of the rolling bearing 4 and the outer ring / inner ring should be a negative gap. Indispensable. Therefore, as a method of setting the preload in this conventional device, the distance between the outer rings is provided with a projection 6a so that the distance between the outer rings is made constant, and the inner cylindrical portion is made in a state where a constant load is applied in the direction in which the inner rings come closer. The inner ring 2 is bonded and fixed. Other than the bonding under such a load state, for example, a spring or a weight may be used.

[0005]

However, the above-mentioned conventional preloading method has the following problems. First, the inner cylindrical portion 2 and the fixing screw 8 extend in the axial direction due to thermal expansion or the like, whereby the distance between the rolling bearings 4 forming a pair increases, and a preload fluctuation due to a temperature change occurs in actual use. Resulting in. Therefore, there is a problem that a desired rotation accuracy is not obtained. Due to the fluctuation of the preload, abnormal noise and resonance occur together with the shaft deflection, and high rotation cannot be expected due to slippage.

Accordingly, an object of the present invention is to solve the above-mentioned problems, and it is possible to prevent a preload applied to a rolling bearing from fluctuating due to a temperature change during actual use, thereby providing an excellent bearing regardless of a temperature change. An object of the present invention is to provide a variable preload bearing unit that can maintain its capacity, can easily change and adjust the preload, and can easily avoid resonance with an assembled product.

[0007]

The object of the present invention is to provide a bearing unit in which an even number of rolling bearings are held between an outer cylindrical portion and an inner cylindrical portion, wherein the outer cylindrical portion or the inner cylindrical portion is provided. An electrostrictive element disposed on one axial end face of the portion, and voltage control means for controlling a voltage applied to the electrostrictive element, and any one of the cylindrical portions provided with the electrostrictive element is provided. At both end surfaces in the axial direction, the electrostrictive element and the electrostrictive element are sandwiched and fixed to the bearing unit mounting portion, and the electrostrictive element is extended.
This is achieved by a bearing unit that is preloaded by contraction.

According to the above construction, between the bearing unit mounting portion on the desired device and the inner or outer cylindrical portion end face, or between the other end surface of the inner or outer cylindrical portion and the bearing unit mounting portion of the desired device. The voltage application control can be performed on the electrostrictive element provided during the period. A preload is applied in the axial direction of the inner or outer cylindrical portion due to the expansion and contraction of the electrostrictive element when such a voltage is applied, and the distance between the outer ring or the inner ring of the paired bearings can be changed. Therefore, the preload adjustment is performed by adjusting this voltage. The preload applied to such a rolling bearing can be easily changed / adjusted by adjusting the voltage applied to the electrostrictive element after installing the variable preload bearing unit for any device to which the present invention is applied. .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A variable preload bearing unit 10 according to one embodiment of the present invention will be described below in detail with reference to FIG. The preload variable bearing unit 10 according to this embodiment includes:
For example, it is a bearing unit used for supporting a precision rotating part such as a spindle motor, a rotary actuator, and a rotary encoder used in a video tape recorder, a hard disk drive, a laser beam printer, and the like.

The preload variable bearing unit 10 basically includes an electrostrictive element 12 as a preload means for applying an axial preload to the inner cylindrical portion 2 and a voltage control device 13 in the bearing unit 1 shown in FIG. The other configuration is the same as that of FIG. That is, the preload variable bearing unit 10 includes the inner cylindrical portion 2 and the outer cylindrical portion 6 rotatably supported on the outer circumference of the inner cylindrical portion 2 via the rolling bearing 4 fitted on the outer circumference of the inner cylindrical portion 2. , And the electrostrictive element 12.

Then, a base 7 serving as a fixing portion of the rotating device is provided.
The fixing screw 8 serves as a portion to which the bearing unit 10 is attached. That is, the inner cylindrical portion 2 is fixed to the base 7 by the fixing screw 8.
Fixed to The fixing screw 8 includes a shaft portion 8a through which the inner cylindrical portion 2 is inserted, a screw portion 8b which is provided at a distal end of the shaft portion 8a and is screwed to the screw portion 7a of the base 7, and a base end of the shaft portion 8a. Equipped head 8c for holding down the end face of inner cylindrical portion 2
Are integrally formed. Further, the outer cylindrical portion 6 serves as a portion for supporting the above-described precision rotating portion (for example, a rotation driving portion of a magnetic disk or an optical disk).

The electrostrictive element 12 is formed in a ring shape to be fitted on the outer periphery of the shaft portion 8a, and is provided so as to be sandwiched between the head portion 8c of the fixing screw 8 and the inner cylindrical portion 2. .
The electrostrictive element 12 is an element that expands and contracts in the axial direction of the inner cylindrical portion 2 according to an applied voltage. When the electrostrictive element 12 is supplied as a part of the variable preload bearing unit 10, the electrostrictive element 12 is bonded to the axial end face of the inner cylindrical portion 2. The voltage control device 13 controls a voltage applied to the electrostrictive element 12 via the lead wire 14. Actually, a temperature change of the inner cylindrical portion 2 and the fixing screw 8 is detected by a temperature sensor (not shown) or the like, and the voltage applied to the electrostrictive element 12 is controlled in accordance with the temperature change, thereby setting the inner ring distance to a predetermined value. And the preload can be stabilized. The voltage control device 13 includes a preload variable bearing unit 1
For example, a power supply or the like attached to a product in which 0 is assembled may be used.

In the variable preload bearing unit 10 described above, the initial preload applied to the inner cylindrical portion 2 at the time of assembling the product is set to be relatively low. Specifically, the preload is set by adjusting the tightening load of the fixing screw 8 or the like. Give. In the case of the present embodiment, a back-mounted configuration is applied, and the setting of the preload is the same as that of the conventional device, and the interval between the outer rings of the paired bearings is not approached at all by providing the protrusion 6a. The inner ring is bonded and fixed to the inner cylindrical portion 2 while applying a certain load in a direction approaching the inner ring. During operation of the precision rotating device product, a prescribed voltage is applied from the voltage controller 13 to the electrostrictive element 12 to expand and contract the electrostrictive element 12, and the inner side according to the expansion and contraction of the electrostrictive element 12. By adjusting the compression / extension of the cylindrical part in the two axial directions, it is adjusted to the appropriate preload necessary for maintaining the bearing capacity. The specified voltage application from the voltage control device 13 to the electrostrictive element 12 includes generation of an appropriate amount of expansion and contraction for the electrostrictive element 12 including thermal expansion due to the temperature of the inner cylindrical portion 2 and the fixing screw 8 at that time. It is a voltage value that can be caused to be calculated based on data such as the temperature and thermal expansion of the inner cylindrical portion 2 and the fixing screw 8.

Further, when the ambient temperature rises during the operation of the product, the pre-load acting on the inner cylindrical portion 2 is raised to a raised temperature so as not to decrease due to the thermal expansion of the inner cylindrical portion 2 and the fixing screw 8. The voltage applied to the electrostrictive element 12 is controlled accordingly.

With the preload variable bearing unit 10 incorporated in a product, the preload variable bearing unit 10
When the product is in operation, the electrostrictive element 1
Change the voltage applied to 2. The change in the applied voltage changes the amount of expansion and contraction of the electrostrictive element 12, and accordingly the length of the inner cylindrical portion 2 in the axial direction changes, so that the resonance point of the preload variable bearing unit 10 with respect to the product can be shifted. Resonance with the product of the variable preload bearing unit 10 can be avoided.

That is, in the preload variable bearing unit 10 of the above-described embodiment, the electrostrictive element 1 according to the temperature change during use.
By expanding and contracting 2, it is possible to substantially prevent the preload acting on the inner cylindrical portion 2 from fluctuating due to a temperature change during use, and to maintain excellent bearing performance regardless of the temperature change. Can be. Further, since the preload can be easily changed and adjusted by adjusting the voltage applied to the electrostrictive element 12, resonance with the assembled product can be easily avoided by changing the preload. The inconvenience of preparing the bearing unit can be solved. In the above-described embodiment, the electrostrictive element 12 is provided between the head of the fixing screw 8 and the inner cylindrical portion 2.
Even if the electrostrictive element 12 is provided between the inner cylindrical portion 2 and the base 7, the same operation and effect can be obtained.

Further, the rotating member is on the inner ring side (the inner cylindrical portion 2).
FIG. 2 shows an embodiment provided in 2). The electrostrictive element 32 may be provided between the protrusion 26 a of the outer cylindrical portion 26 and the bearing 24. In this case, the preload adjusting function is provided on the outer ring side which is the fixed side. The preload adjustment is performed in the same stroke as that performed for the inner cylindrical portion 2 shown in the embodiment of FIG.

The number of rolling bearings provided between the inner cylindrical portion and the outer cylindrical portion and the structure of the rolling bearings are as follows.
The present invention is not limited to the above embodiments. The design can be changed as appropriate without departing from the spirit of the present invention.

[0019]

According to the variable preload bearing unit of the present invention, the electrostriction element is provided between any one of the cylindrical end faces and the bearing unit mounting portion on the desired device, and the voltage application is controlled. The preload adjustment of the paired bearings can be performed. By adjusting the preload applied to such a rolling bearing, it is possible to suppress the preload from fluctuating due to a temperature change during actual use, and to maintain excellent bearing performance regardless of the temperature change. Changes and adjustments can be made easily, and resonance with the assembled product can be easily avoided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of one embodiment of a preload variable bearing unit according to the present invention.

FIG. 2 is a longitudinal sectional view of another embodiment of the variable preload bearing unit according to the present invention.

FIG. 3 is a longitudinal sectional view of a conventional bearing unit.

[Description of Signs] 1 Bearing unit 2, 22 Inner cylindrical part 4, 24 Rolling bearing 6, 26 Outer cylindrical part 6a 26a Projection part 7 Base 8 Fixing screw 10 Preload variable bearing unit 12, 32 Electrostrictive element 13 Voltage controller

Claims (1)

[Claims] 1. A bearing unit in which an even number of rolling bearings are held between an outer cylindrical portion and an inner cylindrical portion, wherein the bearing unit is disposed on one axial end surface of the outer cylindrical portion or the inner cylindrical portion. An electrostrictive element, and voltage control means for controlling a voltage applied to the electrostrictive element, and any one of the cylindrical portions provided with the electrostrictive element is provided along with the electrostrictive element at both axial end surfaces thereof. A bearing unit which is fixedly held by the bearing unit mounting portion and is preloaded adjusted by extension and contraction of the electrostrictive element.